Anogenital Contact Dermatitis in Spain: A REIDAC Study of Patients Undergoing Patch Testing in 2019-2024

Abstract

BACKGROUND: The REIDAC (Spanish Registry for Research in Contact Dermatitis) conducts nationwide epidemiological surveillance of contact dermatitis in Spain. Anogenital involvement within REIDAC has not been previously studied. OBJECTIVES: To describe the most common diagnoses and update relevant allergens in patients with anogenital lesions referred for patch testing. METHODS: We analysed patients who underwent patch testing within REIDAC from 2019 to 2024. Patients were classified into three groups: (G1) exclusively anogenital lesions, (G2) no anogenital involvement and (G3) both anogenital and non-anogenital lesions. Sensitisation and relevance were assessed. RESULTS: Among 18 291 patients, 116 (0.6%) had exclusively anogenital lesions, 17 576 (96.1%) had no anogenital involvement and 599 (3.3%) had both. G1 patients were more likely to have at least one positive reaction (91.4%), a current relevant reaction (53.4%, diagnosed with allergic contact dermatitis, ACD) and to be polysensitised compared to other groups (p < 0.001). 14.5% of anogenital ACD identified cases were not identified by the Spanish baseline series. Fragrances, preservatives, topical anaesthetics and steroids were the leading relevant allergens. Benzisothiazolinone, sodium metabisulfite and propolis emerged as new sensitisers. CONCLUSION: ACD was highly prevalent among patients with anogenital lesions referred for patch testing. The threshold for patch testing in these patients may need reconsideration.